MCP79412 datasheet(42/66 Pages) MICROCHIP

42 / 66 page

MCP79410/MCP79411/MCP79412

DS20002266H-page 42

 2010-2016 Microchip Technology Inc.

6.2.5

EEPROM CURRENT ADDRESS

READ

The MCP7941X contains an address counter that

maintains the address of the last byte accessed,

internally incremented by one. Therefore, if the

previous read access was to address n (n is any legal

address), the next current address read operation

would access data from address n + 1.

Upon receipt of the control byte with R/W bit set to ‘1’,

the MCP7941X issues an Acknowledge and transmits

the 8-bit data word. The master will not acknowledge

the transfer, but generate a Stop condition, and the

MCP7941X discontinues transmission (Figure 6-9).

FIGURE 6-9:

EEPROM CURRENT

ADDRESS READ

6.2.6

EEPROM RANDOM READ

Random read operations allow the master to access

any EEPROM location in a random manner. To perform

this type of read operation, first the address must be

set.

This is done by sending the address to the MCP7941X

as part of a write operation (R/W bit set to ‘0’). After the

address is sent, the master generates a Start condition

following the Acknowledge. This terminates the write

operation, but not before the internal Address Pointer is

set. Then, the master issues the control byte again but

with the R/W bit set to a ‘1’. The MCP7941X will then

issue an Acknowledge and transmit the 8-bit data word.

The master will not acknowledge the transfer but it

does generate a Stop condition which causes the

MCP7941X to discontinue transmission (Figure 6-10).

After a random Read command, the internal address

counter will point to the address location following the

one that was just read.

6.2.7

EEPROM SEQUENTIAL READ

Sequential reads are initiated in the same way as a

random read except that after the MCP7941X transmits

the first data byte, the master issues an Acknowledge

as opposed to the Stop condition used in a random

read. This Acknowledge directs the MCP7941X to

transmit the next sequentially addressed 8-bit word

(Figure 6-11). Following the final byte transmitted to the

master, the master will NOT generate an Acknowledge

but will generate a Stop condition. To provide

sequential reads, the MCP7941X contains an internal

Address Pointer which is incremented by one at the

completion of each operation. This Address Pointer

allows the entire EEPROM block to be serially read

during one operation. The internal Address Pointer will

automatically roll over from address 0x7F to address

0x00 if the master acknowledges the byte received

from address 0x7F.

FIGURE 6-10:

EEPROM RANDOM READ

FIGURE 6-11:

EEPROM SEQUENTIAL READ

Note:

The Address Pointer is shared between

the SRAM/RTCC registers and the

EEPROM.

BUS ACTIVITY

MASTER

SDA LINE

BUS ACTIVITY

CONTROL

BYTE

DATA

BYTE

11 1

BUS ACTIVITY

MASTER

SDA LINE

BUS ACTIVITY

CONTROL

BYTE

ADDRESS

BYTE

CONTROL

BYTE

DATA

BYTE

S 101 0

111

S 1 010

11 1

BUS ACTIVITY

MASTER

SDA LINE

BUS ACTIVITY

CONTROL

BYTE

DATA n

DATA n + 1

DATA n + 2

DATA n + X

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